It was at about the same epoch that Lebon was put upon the track of lighting by gas, during a sojourn at Brachay.  He one day threw a handful of sawdust into a glass vial that he heated over a fire.  He observed issuing from the bottle a dense smoke which suddenly caught fire and produced a beautiful luminous flame.  The inventor understood the importance of the experiment that he had just performed, and resolved to work it further.  He had just found that wood and other combustibles were, under the action of heat, capable of disengaging a gas fit for lighting and heating.  He had seen that the gas which is disengaged from wood is accompanied with blackish vapors of an acrid and empyreumatic odor.  In order that it might serve for the production of light, it was necessary to free it from these foreign products.

Lebon passed the vapor through a tube into a flask of water, which condensed the tarry and acid substances, and the gas escaped in a state of purity.  This modest apparatus was the first image of the gas works; and it comprised the three essential parts thereof—­the generating apparatus, the purifying apparatus, and the receiver for collecting the gas.

One year afterward, the inventor had seen Fourcroy, Prony, and the great scientists of his epoch.  On the 28th of September, 1799, he took out a patent in which he gives a complete description of his thermo lamp, by means of which he produced a luminous gas, while at the same time manufacturing wood tar and pyroligneous or acetic acid.  In this patent he mentions coal as proper to replace wood, and he explains his system with a visible emotion and singular ardor.  In reading what he has written we are struck with that form of persuasion that does not permit of doubting that he foresaw the future in reserve for his system.

Unfortunately, Lebon could not devote all his time to his discovery.  Being a government engineer, without money and fortune, he had to attend to his duties.  He went as an ordinary engineer to Angouleme, but he did not forget his illuminating gas, and he strongly regretted Paris, which he termed “an incomparable focus of study.”  He devoted himself to mathematics and science, he made himself beloved by all, and his mind wandered far from his daily occupation.  The engineer in chief soon complained of him, but a committee appointed to investigate the charges that had been made against him affirmed that he was free from any reproach.  He was sent back to his post, but war was decimating the resources of France, and the republic, while Bonaparte was in Italy, no longer had any time to pay its engineers.  Lebon wrote some pressing letters to the minister, asking for the sums due on his work, but all of them remained without reply.  His wife went to Paris, but her applications were fruitless.  She wrote herself to the minister the following letter, which exists in the archives of the School of Bridges and Roads: 

    “Liberty, equality, fraternity—­Paris. 22 Messidor, year VII. of
    the French Republic, one and indivisible—­the wife of Citizen
    Lebon to Citizen Minister of the Interior: